Color-filter device

ABSTRACT

A micro-transfer color-filter device comprises a color filter, an electrical conductor disposed in contact with the color filter, and at least a portion of a color-filter tether attached to the color filter or structures formed in contact with the color filter. In certain embodiments, a color filter is a variable color filter electrically controlled through one or more electrodes and can be responsive to heat, electrical current, or an electrical field to modify its optical properties, such as color, transparency, absorption, or reflection. In certain embodiments, A color-filter device includes connection posts and can be provided in or on a source wafer suitable for micro-transfer printing. In some embodiments, a color-filter device is disposed on a device substrate and can include a control circuit for controlling the color filter. An array of micro-transfer color-filter devices can be disposed on a display substrate in order to form a display.

PRIORITY APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/461,871, filed Mar. 17, 2017, entitled Micro-TransferPrinted LED and Color Filter Structure which claims priority to andbenefit of U.S. Provisional Patent Application No. 62/318,512, filedApr. 5, 2016, entitled Micro-Transfer Printed LED and Color FilterStructure, the disclosure of each of which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to color-filter structures anddevices (e.g., micro-transfer printable color-filter devices).

BACKGROUND OF THE INVENTION

Solid-state electrically controlled light emitters are widely used inthe display and lighting industries. Displays often use differentlycolored emitters, and lighting applications require a large colorrendering index (CRI). In either case, the efficient production of avariety of colors is important.

Colored light is produced in liquid crystal displays (LCDs) and someorganic light-emitting diode (OLED) displays using white-light emitters(such as a backlight) and color filters, for example as taught in U.S.Pat. No. 6,392,340. However, this approach has the disadvantage ofwasting much of the white light produced by the back light. In adifferent approach, light emitters emit a specific desired color. Evenin this case, however, improved color gamut can be achieved by combiningthe light emitters with color filters.

Inorganic displays use arrays of inorganic light emitters, typicallylight-emitting diodes (LEDs). Because of the variability in LEDmaterials and manufacturing processes, different LEDs, even when made insimilar materials, will emit a range of frequencies and groups of LEDs,for example in a display, experience uniformity variations.

Another technique used to provide colored light is color conversion, inwhich a single kind of light emitter is used to optically stimulate(pump) a second light emitter with light having a first energy(frequency). The second light emitter absorbs the first light and thenemits second light having a lower energy (frequency). By choosing avariety of different second light emitters that emit light of differentfrequencies, a display or a solid-state light device can emit light ofdifferent colors. For example, a blue light emitter can be used to emitblue light and to optically pump yellow, red, or green light emitters.U.S. Pat. No. 7,990,058 describes an OLED device with a color-conversionmaterial layer.

Phosphors are often used as color-conversion materials. For example,U.S. Pat. No. 8,450,927 describes an LED lamp using a phosphor and U.S.Pat. No. 7,969,085 discloses a color-change material layer that convertslight of a second frequency range higher than a first frequency range tolight of the first frequency range. Light-emissive inorganic core/shellnano-particles (quantum dots or QDs) are also used to produce opticallypumped or electrically stimulated colored light, for example as taughtin U.S. Pat. No. 7,919,342.

Color conversion materials can be deposited and formed in structuressimilar to those of color filters. Color filters, pigments, phosphors,and quantum dots, however, can be expensive. There remains a need,therefore, for structures and methods that improve manufacturingefficiency and performance uniformity in the production of colored lightin a simple and robust structure made with fewer parts and lessmaterial.

SUMMARY OF THE INVENTION

The present invention provides light-emitting, filtering, orlight-converting structures and displays with reduced costs in robuststructures made through efficient manufacturing processes using reducedquantities of materials. In this invention, the term ‘color filter’ canrefer to: (i) A structure that filters light by absorbing at least aportion of some of the frequencies of the light and transmitting atleast a portion of some of the frequencies of the light. Typically, thefrequency of most of the absorbed light is different from the frequencyof most of the transmitted light. Pigments and dyes embedded in a layerof material, such as transparent resin, are often used to form such astructure; and (ii) A structure that changes the frequency of at leastsome of the light by absorbing and at least a portion of some of thefrequencies of the light and emitting light of a different frequency andof a lower energy thereby converting at least some of the light from ahigher frequency to a lower frequency. Phosphors and quantum dots aretypically embedded in a layer of material, such as a transparent resinand can be used to make a light-conversion structure. Doped or undopedsemiconductor crystals can also be used in light-conversion structures.Thus, in this disclosure, the term ‘color filter’ refers to a structurethat filters light or converts light, or both, and can be or include oneor more of: a curable resin, a dye, a pigment, a color-conversionmaterial, a semiconductor crystal, a phosphor, and a quantum dot.

In certain embodiments, a micro-transfer printed color-filter structurecomprises a color filter and a fractured color-filter tether attached tothe color filter. The fractured color-filter tether can include at leastsome of the same material as the color filter or can include a portionof an encapsulation layer. In related embodiments, a color-filter sourcewafer comprises a source wafer having a patterned sacrificial layerincluding sacrificial portions separated by anchors, a patterned colorfilter layer having a color filter disposed entirely on each sacrificialportion, and one or more color-filter tethers physically connecting eachcolor filter to an anchor. In embodiments, the source wafer is orincludes a glass, a polymer, a semiconductor, or silicon, thesacrificial portions are a designated portion of an anisotropicallyetchable silicon, a selectively etchable material, or a gap between thepixel structure and the source wafer, or any combination of these. In anembodiment, the fractured color-filter tether includes at least some ofthe same material as the color filter or an encapsulation layer.

In certain embodiments, a method of making a color-filter source wafercomprises providing a source wafer having a patterned sacrificial layerincluding sacrificial portions separated by anchors, disposing a colorfilter layer on the wafer, and patterning a color filter entirely oneach sacrificial portion. In an embodiment, the sacrificial portion isetched to form one or more color-filter tethers physically connectingeach color filter to an anchor. In another embodiment, the color filteris micro-transfer printed from the color-filter source wafer to adestination substrate, such as a display substrate.

In certain embodiments, a micro-transfer printed pixel structurecomprises an LED having a light-emitting side, a color filter disposedadjacent to the light-emitting side of the LED, and a fractured pixeltether physically attached to the LED or a fractured pixel tetherphysically attached to the LED or to the color filter, or both. Thefractured pixel tether can include at least some of the same material asthe color filter, at least some of the same material as the LED, atleast some of the material in an encapsulation layer, or any one or allof these.

In certain embodiments, a pixel structure source wafer comprises asource wafer having a patterned sacrificial layer including sacrificialportions separated by anchors, an LED disposed entirely on or over eachsacrificial portion, the LED having a light-emitting side, a colorfilter disposed adjacent to the light-emitting side of the LED, thecolor filter disposed entirely on or over each sacrificial portion, andone or more pixel tethers physically connecting each LED or color filterto an anchor. In various embodiments, the source wafer is or includes aglass, a polymer, a semiconductor, or silicon, the sacrificial portionsare a designated portion of an anisotropically etchable silicon, aselectively etchable material, or a gap between the pixel structure andthe source wafer, or any one of or combination of these. The fracturedpixel tether can include at least some of the same material as the colorfilter, can include at least some of the same material as the LED, caninclude a portion of an encapsulation layer, or any one or all of these.

In certain embodiments, a method of making a pixel structure sourcewafer comprises providing a source wafer having a patterned sacrificiallayer including sacrificial portions separated by anchors, disposing anLED entirely on or over each sacrificial portion, the LED having alight-emitting side, and providing a color filter adjacent to thelight-emitting side of each LED, the color filter disposed entirely onor over each sacrificial portion to form a pixel structure. The colorfilter can be micro-transfer printed from a color-filter source waferonto the source wafer entirely over the sacrificial portion and an LEDmicro-transfer printed from an LED source wafer onto the color filter sothat the color filter is disposed adjacent to the light-emitting side ofthe LED. Alternatively, an LED is micro-transfer printed from an LEDsource wafer onto the source wafer entirely over the sacrificial portionand a color filter is micro-transfer printed from a color-filter sourcewafer onto the LED so that the color filter is disposed adjacent to thelight-emitting side of the LED. In another embodiment, an LED ismicro-transfer printed from an LED source wafer onto the source waferentirely over the sacrificial portion and a color filter is formed overthe LED so that the color filter is disposed adjacent to thelight-emitting side of the LED. In yet another embodiment, a colorfilter is formed on the source wafer entirely over the sacrificialportion and an LED is micro-transfer printed from an LED source waferonto the color filter so that the color filter is disposed adjacent tothe light-emitting side of the LED. In further embodiments, thesacrificial portion is etched to form one or more pixel tethersphysically connecting each pixel structure to an anchor or a pixelstructure is micro-transfer printed from the pixel structure sourcewafer to a destination substrate.

In certain embodiments, a micro-transfer printed intermediate structurecomprises an intermediate substrate, one or more pixel structuresdisposed on the intermediate substrate, each pixel structure includingan LED having a light-emitting side, a color filter disposed adjacent tothe light-emitting side of the LED, and a fractured pixel tetherphysically attached to the LED or to the color filter, or both, and afractured intermediate tether physically attached to the intermediatesubstrate. The intermediate substrate can be or include a glass, apolymer, a semiconductor, or silicon, or any one or any combination ofthese. The fractured pixel tether can include at least some of the samematerial as the color filter, at least some of the same material as theLED, at least some of the material in an encapsulation layer, or any oneor all of these. The fractured intermediate tether can include at leastsome of the same material as the color filter, at least some of the samematerial as the intermediate substrate, at least some of the material inan encapsulation layer, or any one or all of these.

In certain embodiments, an intermediate structure source wafer comprisesa source wafer having a patterned sacrificial layer includingsacrificial portions separated by anchors, a patterned intermediatesubstrate layer disposed over the patterned sacrificial layer formingseparate and independent intermediate substrates, each intermediatesubstrate disposed entirely over a sacrificial portion, one or morepixel structures disposed entirely on each intermediate substrate, eachpixel structure including an LED, the LED having a light-emitting side,and a color filter disposed adjacent to the light-emitting side of theLED, one or more fractured pixel tethers physically attached to eachpixel structure, and a fractured intermediate tether physically attachedto the intermediate substrate.

In certain embodiments, the source wafer is or includes a glass, apolymer, a semiconductor, or silicon, the intermediate substrate is orincludes a glass, a polymer, a semiconductor, or silicon, thesacrificial portions are a designated portion of an anisotropicallyetchable silicon, a selectively etchable material, or a gap between theintermediate substrate and the source wafer, or any one or anycombination of these. The fractured pixel tether can include at leastsome of the same material as the color filter, at least some of the samematerial as the LED, at least some of the material in an encapsulationlayer, or any one or all of these. The intermediate tether can includeat least some of the same material as the color filter, at least some ofthe same material as the intermediate substrate, at least some of thematerial in an encapsulation layer, or any one or all of these. In yetanother embodiment, the intermediate tether includes at least some ofthe same material as the source wafer or the intermediate substrateincludes at least a portion of the color filter or the color filtermakes up a portion of the intermediate substrate.

In certain embodiments, a method of making an intermediate structuresource wafer comprises providing a source wafer having a patternedsacrificial layer including sacrificial portions separated by anchors,disposing an intermediate substrate over the patterned sacrificiallayer, and disposing one or more pixel structures on the intermediatesubstrate entirely on or over each sacrificial portion, each pixelstructure including an LED having a light-emitting side, a color filterdisposed adjacent to the light-emitting side of the LED, and a fracturedpixel tether physically attached to the pixel structure to form anintermediate structure. In an embodiment, each pixel structure ismicro-transfer printed as a unit from a pixel structure source waferonto the intermediate substrate entirely over the sacrificial portion.In another embodiment, one or more pixel structures are disposed on theintermediate substrate entirely on or over each sacrificial portion bymicro-transfer printing a color filter from a color-filter source waferonto the intermediate substrate of the source wafer entirely over thesacrificial portion and micro-transfer printing an LED from an LEDsource wafer onto the color filter so that the color filter is disposedadjacent to the light-emitting side of the LED. In another embodiment,an LED is micro-transfer printed from an LED source wafer onto theintermediate substrate of the source wafer entirely over the sacrificialportion and a color filter is micro-transfer printed from a color-filtersource wafer onto the LED so that the color filter is disposed adjacentto the light-emitting side of the LED. In yet another embodiment, an LEDis micro-transfer printed from an LED source wafer onto the source waferentirely over the sacrificial portion and a color filter is formed overthe LED so that the color filter is disposed adjacent to thelight-emitting side of the LED. In an alternative embodiment, a colorfilter is formed on the source wafer entirely over the sacrificialportion and an LED is micro-transfer printed from an LED source waferonto the color filter so that the color filter is disposed adjacent tothe light-emitting side of the LED. In further embodiments, thesacrificial portion is etched to form one or more intermediate tethersphysically connecting each intermediate structure to an anchor or anintermediate structure is micro-transfer printed from the intermediatestructure source wafer to a destination substrate.

In certain embodiments, an LED display comprises a display substrate anda plurality of pixel structures disposed on the display substrate. Eachpixel structure includes one or more LEDs and a color filtercorresponding to each LED. Each LED has a light-emitting side and eachcolor filter is disposed adjacent to the light-emitting side of thecorresponding LED. In various embodiments, each color filter is locatedbetween the display substrate and an LED, each LED is located betweenthe display substrate and a color filter, each LED is a micro-transferprinted LED having a fractured LED tether physically attached to theLED, each color filter is a micro-transfer printed color filter having afractured color-filter tether physically attached to the color filter,each pixel structure is a micro-transfer printed pixel structure havinga fractured pixel tether, or each pixel structure is a micro-transferprinted intermediate structure having a fractured intermediate tether.

In certain embodiments, a method of making an LED display comprisesproviding a display substrate and disposing a plurality of pixelstructures on the display substrate. Each pixel structure includes oneor more LEDs, for example inorganic LEDs, and a color filtercorresponding to each LED. Each LED has a light-emitting side and eachcolor filter is disposed adjacent to the light-emitting side of thecorresponding LED. Each LED can be a micro-transfer printed LED having afractured LED tether physically attached to the LED. The pixel structurecan be disposed on the display substrate by micro-transfer printing acolor filter from a color-filter source wafer onto the display substrateand micro-transfer printing an LED from an LED source wafer onto thecolor filter so that the color filter is disposed adjacent to thelight-emitting side of the LED.

Alternatively, an LED can be micro-transfer printed from an LED sourcewafer onto the display substrate and a color filter micro-transferprinted from a color-filter source wafer onto the LED so that the colorfilter is disposed adjacent to the light-emitting side of the LED. Inanother embodiment, an LED can be micro-transfer printed from an LEDsource wafer onto the display substrate and a color filter formed overthe LED so that the color filter is disposed adjacent to thelight-emitting side of the LED. In yet another embodiment, a colorfilter is formed on the display substrate and an LED micro-transferprinted from an LED source wafer onto the color filter so that the colorfilter is disposed adjacent to the light-emitting side of the LED. In analternative embodiment, a pixel structure is micro-transfer printed froma pixel structure source wafer onto the intermediate substrate of thesource wafer entirely over the sacrificial portion. In an embodiment, anintermediate structure is micro-transfer printed from an intermediatestructure source wafer onto the display substrate.

In one aspect, the disclosed technology includes a micro-transferprinted color-filter structure, including: a color filter; and afractured color-filter tether attached to the color filter or layersformed in contact with the color filter.

In certain embodiments, the color filter is or includes one or more of:a curable resin, a dye, a pigment, a color-conversion material, asemiconductor crystal, a phosphor, and a quantum dot.

In certain embodiments, the fractured color-filter tether includes atleast some of the same material as the color filter or furthercomprising an encapsulation layer and wherein the fractured color-filtertether includes at least some of the same material as the encapsulationlayer or at least a portion of the encapsulation layer forms thecolor-filter tether.

In another aspect, the disclosed technology includes a color-filtersource wafer, including: a source wafer having a patterned sacrificiallayer including sacrificial portions separated by anchors; a patternedcolor-filter layer including a color filter disposed entirely on or overeach sacrificial portion; and one or more color-filter tethersphysically connecting each color filter, or layers formed in contactwith the color filter, to an anchor.

In certain embodiments, (i) the color filter is or includes one or moreof: a curable resin, a dye, a pigment, a color conversion material, asemiconductor crystal, a phosphor, or a quantum dot; (ii) the sourcewafer is or includes a glass, a polymer, a semiconductor, or silicon;(iii) the sacrificial portions are a designated portion of ananisotropically etchable silicon, a selectively etchable material, or agap between the color filter and the source wafer; or any one or anycombination of (i), (ii), and (iii).

In certain embodiments, the color-filter tether includes at least someof the same material as the color filter or comprising an encapsulationlayer encapsulating the color filter and wherein the color-filter tetherincludes at least some of the same material as the encapsulation layeror at least a portion of the encapsulation layer forms the color-filtertether.

In another aspect, the disclosed technology includes a method of makinga color-filter source wafer, including: providing a source wafer havinga patterned sacrificial layer including sacrificial portions separatedby anchors; disposing a color filter layer on or over the wafer; andpatterning a color filter entirely on or over each sacrificial portion.

In certain embodiments, the method includes disposing an encapsulationlayer encapsulating the color filter.

In certain embodiments, the method includes etching the sacrificialportion to form one or more color-filter tethers physically connectingeach color filter, or layers formed in contact with the color filter, toan anchor.

In certain embodiments, the method includes micro-transfer printing acolor filter from the color-filter source wafer to a destinationsubstrate.

In another aspect, the disclosed technology includes a micro-transferprinted pixel structure, including: an LED having a light-emitting side;a color filter disposed adjacent to the light-emitting side of the LED;and a fractured pixel tether physically attached to the LED or layersdisposed on or in contact with the LED, or a fractured pixel tetherphysically attached to the color filter or layers disposed on the colorfilter.

In certain embodiments, the color filter is or includes one or more of:a curable resin, a dye, a pigment, a color conversion material, asemiconductor crystal, a phosphor, and a quantum dot.

In certain embodiments, the fractured pixel tether includes at leastsome of the same material as the color filter, wherein the fracturedpixel tether includes at least some of the same material as the LED, orboth, or comprising an encapsulation layer encapsulating the LED andcolor filter that forms the fractured pixel tether or the fracturedpixel tether is a part of or is attached to the encapsulation layer.

In another aspect, the disclosed technology includes a pixel structuresource wafer, including: a source wafer having a patterned sacrificiallayer including sacrificial portions separated by anchors; an LEDdisposed entirely on or over each sacrificial portion, the LED having alight-emitting side; a color filter disposed adjacent to thelight-emitting side of the LED, the color filter disposed entirely on orover each sacrificial portion; and one or more pixel tethers physicallyconnecting each LED or color filter to an anchor.

In certain embodiments, (i) the color filter is or includes one or moreof: a curable resin, a dye, a pigment, a color conversion material, asemiconductor crystal, a phosphor, or a quantum dot; (ii) the sourcewafer is or includes a glass, a polymer, a semiconductor, or silicon;(iii) the sacrificial portions are a designated portion of ananisotropically etchable silicon, a selectively etchable material, or agap between the pixel structure and the source wafer; or any one or anycombination of (i), (ii), and (iii).

In certain embodiments, the pixel tether includes at least some of thesame material as the color filter or wherein the fractured pixel tetherincludes at least some of the same material as the LED, or both, orcomprising an encapsulation layer encapsulating the color filter and LEDand wherein the pixel tether includes at least some of the same materialas the encapsulation layer or at least a portion of the encapsulationlayer forms the pixel tether or the pixel tether is a part of or isattached to the encapsulation layer.

In another aspect, the disclosed technology includes a method of makinga pixel structure source wafer, including: providing a source waferhaving a patterned sacrificial layer including sacrificial portionsseparated by anchors; disposing an LED entirely on or over eachsacrificial portion, the LED having a light-emitting side; and disposinga color filter adjacent to the light-emitting side of each LED, thecolor filter disposed entirely on or over each sacrificial portion toform a pixel structure.

In certain embodiments, the method includes (i) micro-transfer printinga color filter from a color-filter source wafer onto the source waferentirely over the sacrificial portion and micro-transfer printing an LEDfrom an LED source wafer onto the color filter so that the color filteris disposed adjacent to the light-emitting side of the LED; (ii)micro-transfer printing an LED from an LED source wafer onto the sourcewafer entirely over the sacrificial portion and dispose a color filterfrom a color-filter source wafer onto the LED so that the color filteris disposed adjacent to the light-emitting side of the LED; (iii)micro-transfer printing an LED from an LED source wafer onto the sourcewafer entirely over the sacrificial portion and forming a color filterover the LED so that the color filter is disposed adjacent to thelight-emitting side of the LED; (iv) forming a color filter on thesource wafer entirely over the sacrificial portion and micro-transferprinting an LED from an LED source wafer onto the color filter so thatthe color filter is disposed adjacent to the light-emitting side of theLED; or (v) encapsulating the LED and color filter with an encapsulationlayer, the encapsulation layer forming a part of the pixel tether or thepixel tether including material from the encapsulation layer.

In certain embodiments, the method includes etching the sacrificialportion to form one or more pixel tethers physically connecting eachpixel structure to an anchor.

In certain embodiments, the method includes micro-transfer printing apixel structure from the pixel structure source wafer to a destinationsubstrate.

In another aspect, the disclosed technology includes a micro-transferprinted intermediate structure, including: an intermediate substrate;one or more pixel structures disposed on or over the intermediatesubstrate, each pixel structure including an LED having a light-emittingside, a color filter disposed adjacent to the light-emitting side of theLED, and a fractured pixel tether physically attached to the pixelstructure; and a fractured intermediate tether physically attached tothe intermediate substrate or physically attached to a layer disposed onthe intermediate substrate.

In certain embodiments, (i) the color filter is or includes one or moreof: a curable resin, a dye, a pigment, a color conversion material, asemiconductor crystal, a phosphor, or a quantum dot; (ii) theintermediate substrate is or includes a glass, a polymer, asemiconductor, or silicon; or any one or any combination of (i), and(ii).

In certain embodiments, the fractured pixel tether includes at leastsome of the same material as the color filter or wherein the fracturedpixel tether includes at least some of the same material as the LED, orboth, or comprising an encapsulation layer encapsulating the colorfilter and LED and wherein the pixel tether includes at least some ofthe same material as the encapsulation layer or at least a portion ofthe encapsulation layer forms the pixel tether or the pixel tether is apart of or is attached to the encapsulation layer.

In certain embodiments, the fractured intermediate tether includes atleast some of the same material as the color filter or wherein thefractured intermediate tether includes at least some of the samematerial as the intermediate substrate, or both, or comprising anencapsulation layer encapsulating the color filter and LED and whereinthe intermediate tether includes at least some of the same material asthe encapsulation layer or at least a portion of the encapsulation layerforms the intermediate tether or the intermediate tether is a part of oris attached to the encapsulation layer.

In another aspect, the disclosed technology includes an intermediatestructure source wafer, including: a source wafer having a patternedsacrificial layer including sacrificial portions separated by anchors; apatterned intermediate substrate layer disposed on or over the patternedsacrificial layer forming separate and independent intermediatesubstrates, each intermediate substrate disposed entirely over asacrificial portion; one or more pixel structures disposed entirely oneach intermediate substrate, each pixel structure including an LED, theLED having a light-emitting side, and a color filter disposed adjacentto the light-emitting side of the LED; one or more fractured pixeltethers physically attached to each pixel structure; and an intermediatetether physically attached to the intermediate substrate or a layer onthe intermediate substrate.

In certain embodiments, (i) the color filter is or includes one or moreof: a curable resin, a dye, a pigment, a color conversion material, asemiconductor crystal, a phosphor, or a quantum dot; (ii) the sourcewafer is or includes a glass, a polymer, a semiconductor, or silicon;(iii) the intermediate substrate is or includes a glass, a polymer, asemiconductor, or silicon; (iv) the sacrificial portions are adesignated portion of an anisotropically etchable silicon, a selectivelyetchable material, or a gap between the intermediate substrate and thesource wafer; or any one or any combination of (i), (ii), (iii) and(iv).

In certain embodiments, the fractured pixel tether includes at leastsome of the same material as the color filter or wherein the fracturedpixel tether includes at least some of the same material as the LED, orboth, or comprising an encapsulation layer encapsulating the colorfilter and LED and wherein the pixel tether includes at least some ofthe same material as the encapsulation layer or at least a portion ofthe encapsulation layer forms the pixel tether or the pixel tether is apart of or is attached to the encapsulation layer.

In certain embodiments, the intermediate tether includes at least someof the same material as the color filter, wherein the intermediatetether includes at least some of the same material as the intermediatesubstrate, or wherein the intermediate tether includes at least some ofthe same material as the source wafer, or comprising an encapsulationlayer encapsulating the color filter and LED and wherein theintermediate tether includes at least some of the same material as theencapsulation layer or at least a portion of the encapsulation layerforms the intermediate tether or the intermediate tether is a part of oris attached to the encapsulation layer.

In certain embodiments, the intermediate substrate includes at least aportion of the color filter or the color filter makes up a portion ofthe intermediate substrate.

In another aspect, the disclosed technology includes a method of makingan intermediate structure source wafer, including: providing a sourcewafer having a patterned sacrificial layer including sacrificialportions separated by anchors; disposing an intermediate substrate overthe patterned sacrificial layer; and disposing one or more pixelstructures on the intermediate substrate entirely on or over eachsacrificial portion, each pixel structure including an LED having alight-emitting side, and a color filter disposed adjacent to thelight-emitting side of the LED, and a fractured pixel tether physicallyattached to the pixel structure to form an intermediate structure.

In certain embodiments, the method includes disposing one or more pixelstructures on the intermediate substrate entirely on or over eachsacrificial portion by: (i) micro-transfer printing a color filter froma color-filter source wafer onto the intermediate substrate of thesource wafer entirely over the sacrificial portion and micro-transferprinting an LED from an LED source wafer onto the color filter so thatthe color filter is disposed adjacent to the light-emitting side of theLED; (ii) micro-transfer printing an LED from an LED source wafer ontothe intermediate substrate of the source wafer entirely over thesacrificial portion and micro-transfer printing a color filter from acolor-filter source wafer onto the LED so that the color filter isdisposed adjacent to the light-emitting side of the LED; (iii)micro-transfer printing an LED from an LED source wafer onto the sourcewafer entirely over the sacrificial portion and forming a color filterover the LED so that the color filter is disposed adjacent to thelight-emitting side of the LED; (iv) forming a color filter on thesource wafer entirely over the sacrificial portion and micro-transferprinting an LED from an LED source wafer onto the color filter so thatthe color filter is disposed adjacent to the light-emitting side of theLED; or (v) micro-transfer printing a pixel structure from a pixelstructure source wafer onto the intermediate substrate of the sourcewafer entirely over the sacrificial portion.

In certain embodiments, the method includes etching the sacrificialportion to form one or more intermediate tethers physically connectingeach intermediate structure to an anchor.

In certain embodiments, the method includes micro-transfer printing anintermediate structure from the intermediate structure source wafer to adestination substrate.

In another aspect, the disclosed technology includes an LED display,including: a display substrate; and a plurality of pixel structuresdisposed on the display substrate, each pixel structure including one ormore LEDs, each LED having a light-emitting side, and a color filtercorresponding to each LED, each color filter disposed adjacent to thelight-emitting side of the corresponding LED.

In certain embodiments, each color filter is located between the displaysubstrate and an LED.

In certain embodiments, each LED is located between the displaysubstrate and a color filter.

In certain embodiments, each LED is a micro-transfer printed LED and afractured LED tether is physically attached to the LED.

In certain embodiments, each color filter is a micro-transfer printedcolor filter and a fractured color-filter tether is physically attachedto the color filter.

In certain embodiments, each pixel structure is a micro-transfer printedpixel structure having a fractured pixel tether.

In certain embodiments, each pixel structure is part of an intermediatestructure having a fractured intermediate tether.

In another aspect, the disclosed technology includes a method of makingan LED display, including: providing a display substrate; and disposinga plurality of pixel structures on the display substrate, each pixelstructure including one or more LEDs, each LED having a light-emittingside, and a color filter corresponding to each LED, each color filterdisposed adjacent to the light-emitting side of the corresponding LED.

In certain embodiments, each LED is a micro-transfer printed LED havinga fractured LED tether physically attached to the LED or layers on,over, or in contact with the LED. In certain embodiments, the methodincludes disposing a pixel structure on the display substrate by: (i)micro-transfer printing a color filter from a color-filter source waferonto the display substrate and micro-transfer printing an LED from anLED source wafer onto the color filter so that the color filter isdisposed adjacent to the light-emitting side of the LED; (ii)micro-transfer printing an LED from an LED source wafer onto the displaysubstrate and micro-transfer printing a color filter from a color-filtersource wafer onto the LED so that the color filter is disposed adjacentto the light-emitting side of the LED; (iii) micro-transfer printing anLED from an LED source wafer onto the display substrate and forming acolor filter over the LED so that the color filter is disposed adjacentto the light-emitting side of the LED; (iv) forming a color filter onthe display substrate and micro-transfer printing an LED from an LEDsource wafer onto the color filter so that the color filter is disposedadjacent to the light-emitting side of the LED; (v) micro-transferprinting a pixel structure from a pixel structure source wafer onto theintermediate substrate of the source wafer entirely over the sacrificialportion; or (vi) micro-transfer printing an intermediate structure froman intermediate structure source wafer onto the display substrate.

In some embodiments of the present invention, a color-filter devicecomprises a color filter, an electrical conductor disposed in contactwith the color filter, and at least a portion of a color-filter tetherattached to the color filter or structures formed in contact with orsupporting the color filter. The color filter is a variable color filterand can be electrically controlled. The color filter can be or includeone or more of: a phase-change material, an electrically controlled ink,a gel, a photonic crystal, or a matrix of photonic crystals. Thecolor-filter material can be a phase-change material that can becontrolled to switch from an amorphous state to a crystalline state orfrom a crystalline state to an amorphous state. Each of the amorphousstate and a crystalline state can have a different optical attribute,such as color.

The electrical conductor can be a resistor that heats the color filterin response to an electrical current passed through the resistor and thecolor filter can change the color of light filtered by the color filterin response to heat. The electrical conductor can be substantiallyreflective or transparent and be or comprise a metal or metal alloy.

The color filter can be conductive and generate heat in response to anelectrical current. The resulting heat can change the state of the colorfilter between an amorphous state or a crystalline state and therebychange the color of the color filter.

The color filter can have a first side and a second side opposed to thefirst side, the electrical conductor can be a first electrode disposedon and in direct contact with the first side of the color filter, andcan comprise a second electrode disposed on and in direct contact withthe second side of the color filter. The color filter can change thecolor of light filtered by the color filter in response to an electricalcurrent, in response to a voltage difference provided between the firstand second electrodes, or in response to an electrical field providedbetween the first and second electrodes.

The color filter can be a reflective color filter or a transmissivecolor filter.

The color-filter device can comprise a color-filter substrate on or inwhich the color filters and electrical conductor(s) are disposed. Thecolor-filter substrate can be a semiconductor and can include circuitrysuch as control circuitry. In some embodiments, the color-filtersubstrate is a dielectric, such as silicon dioxide or silicon nitride.

In some embodiments, the color-filter device comprises a capacitor and aswitch forming a control circuit, the switch controllably connecting thecapacitor to the electrical conductor. The color-filter device caninclude a color-filter substrate and the switch and the capacitor canform a control circuit that is disposed on or formed in the color-filtersubstrate and can be located under the color filter.

In some embodiments, the capacitor is charged from an external powersource to a voltage appropriate for color filter material state change.Once the capacitor is charged, the switch is used to connect thecapacitor to the color filter and current passes from the capacitor tothe color filter. The color filter is thereby heated in a controlledmanner and the state of the color filter is changed. Different capacitorinitialization voltages result in different state changes.

In some embodiments, the color-filter device comprises a plurality ofcolor filters. In some embodiments, each color filter of the pluralityof color filters has an electrically separate electrical conductordisposed in contact with the color filter. The color of light filteredby each color filter of the plurality of color filters can be adifferent color of light from the color of light filtered by other colorfilters of the plurality of color filters. Each color-filter device caninclude a corresponding control circuit to control each color filter ora color-filter device can include multiple color filters that each havea corresponding control circuit. The color filters can be stacked orprovided adjacent to each other on the surface of a color-filtersubstrate. In some embodiments, multiple color-filter devices, each witha color-filter tether, are stacked or provided adjacent to each other onthe surface of an intermediate substrate or a destination substrate. Insome embodiments, the intermediate substrate can have an intermediatetether and can be micro-transfer printed.

In some embodiments of the present invention, the color filters caninclude color-filter tethers that are broken by pressure from amicro-transfer stamp when the color filters are micro-transfer printedfrom a source wafer to a destination substrate such as an intermediatesubstrate or display substrate by the micro-transfer stamp. Similarly,the color-filter devices can include intermediate tethers that arebroken when the devices are micro-transfer printed from a source waferto a destination substrate such as a display substrate by themicro-transfer stamp. The color-filter devices can be pixels and thecolor-filter devices can be matrix-address-controlled in a display on adisplay substrate.

In some embodiments, a color-filter device wafer comprises a waferhaving a wafer substrate, the wafer substrate comprising a patternedsacrificial layer including sacrificial portions separated by anchors. Acolor-filter device is disposed entirely over each sacrificial portion.In some embodiments, a plurality of color filters or color-filterdevices are disposed entirely over each sacrificial portion, each colorfilter of the plurality of color filters having an electrically separateelectrical conductor disposed in contact with the color filter, whereinthe color of light filtered by each color filter of the plurality ofcolor filters is a different color of light from the color of lightfiltered by other color filters of the plurality of color filters.

In some embodiments, a color-filter device display comprises a displaysubstrate, a plurality of color-filter devices disposed on the displaysubstrate, wherein each color-filter devices comprises a plurality ofcolor filters, each color filter of the plurality of color filters hasan electrically separate electrical conductor disposed in contact withthe color filter, and wherein the color of light filtered by each colorfilter of the plurality of color filters is a different color of lightfrom the color of light filtered by other color filters of the pluralityof color filters.

In some embodiments, the color-filter device display comprises aplurality of device substrates, each color-filter device disposed on adevice substrate. Each color-filter device can be a pixel.

A method of making a color-filter device display comprises providing acolor-filter device source wafer, providing a display substrate, andmicro-transfer printing the color-filter devices of the color-filterdevice source wafer from the color-filter device source wafer to thedisplay substrate. In some embodiments, a capacitor or switch, or both,is micro-transfer printed to the display substrate in correspondencewith each color-filter device or a capacitor or switch, or both, ismicro-transfer printed to each of the color-filter devices on thecolor-filter device wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects, features, and advantages ofthe present disclosure will become more apparent and better understoodby referring to the following description taken in conjunction with theaccompanying drawings, in which:

FIGS. 1A and 1B are cross sections of alternative color filterembodiments of the present invention;

FIGS. 2A and 2B are cross sections of alternative color-filter sourcewafer embodiments of the present invention corresponding to FIGS. 1A and1B;

FIG. 3 is a flow chart in accordance with embodiments of the presentinvention corresponding to FIGS. 1 and 2;

FIGS. 4A and 4B are cross sections of pixel structures including an LEDand a color filter in embodiments of the present invention;

FIGS. 5A and 5B are cross sections of alternative pixel structure sourcewafer embodiments of the present invention corresponding to FIGS. 4B and4A;

FIGS. 6A, 6B, and 6C are cross sections of alternative pixel structuresource wafer embodiments of the present invention;

FIG. 7 is a flow chart in accordance with embodiments of the presentinvention corresponding to FIGS. 4, 5A, 5B, and 6A-6C;

FIGS. 8A and 8B are cross sections of intermediate structures, eachincluding an intermediate substrate, an LED, and a color filterembodiment of the present invention;

FIGS. 9A and 9B are cross sections of intermediate structure sourcewafer embodiments of the present invention corresponding to FIGS. 8A and8B;

FIGS. 10A and 10B are flow charts in accordance with embodiments of thepresent invention corresponding to FIGS. 8 and 9;

FIGS. 11 and 12 are perspectives illustrating embodiments of the presentinvention;

FIGS. 13 and 14 are flow charts in accordance with display embodimentsof the present invention; and

FIGS. 15-23 are cross sections illustrating various embodiments of thepresent invention;

FIGS. 24A, 24B, and 25 are cross sections of illustrative embodiments ofthe present invention that include one or more electrodes;

FIGS. 26A, 26B, and 26C are control circuit diagrams according toillustrative embodiments of the present invention;

FIGS. 27A and 27B are perspectives according to illustrative embodimentsof the present invention;

FIGS. 28A and 28B are cross sections of micro-transfer printable wafershaving a color-filter device with multiple color filters andcorresponding electrodes in a planar or stacked configuration accordingto illustrative embodiments of the present invention;

FIG. 28C is an cross section of micro-transfer printable wafers havingmultiple color filters in a stacked configuration according toillustrative embodiments of the present invention;

FIGS. 29 and 30 are cross sections of a color-filter device having asingle electrodes having connection posts in a micro-transfer printablewafer according to illustrative embodiments of the present invention;

FIGS. 31-32 are cross sections of a color-filter device having twoelectrodes on a wafer without, and with, connection posts according toillustrative embodiments of the present invention;

FIG. 33 is an cross section of a color-filter device having a controlcircuit on a wafer with connection posts according to illustrativeembodiments of the present invention;

FIG. 34 is a flow chart according to illustrative methods of certainembodiments the present invention.

The features and advantages of the present disclosure will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The figures are not drawn to scalesince the variation in size of various elements in the Figures is toogreat to permit depiction to scale.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide methods and structures forintegrating color filters and light-emitting diodes (LEDs) in displays,for example inorganic light-emitting diodes. The methods and structuresare suitable for micro-transfer printing and reduce the amount ofcolor-filter material used and, in some embodiments, the number ofpatterning steps required.

In this disclosure, the term ‘color filter’ refers to a structure thatchanges the nature or color of light that passes through the colorfilter. For example, the term ‘color filter’ can refer to a structurethat filters light by absorbing at least a portion of some of thefrequencies of the light and transmitting at least a portion of some ofthe frequencies of the light. Typically, the frequency of the majorityof the absorbed light is different from the frequency of the majority ofthe transmitted light. Pigments and dyes embedded in a layer ofmaterial, such as transparent resin, are typically used to form such astructure. In this invention, the term ‘color filter’ can also refer toa structure that changes the frequency of at least some of the light byconverting at least a portion of some of the frequencies of the light tolight of a different frequency and of a lower energy. Phosphors andquantum dots embedded in a layer of material, such as a transparentresin, such as a curable resin, for example, curable by exposure to heator electromagnetic radiation, can provide such a structure. Thus, inthis disclosure, the term ‘color filter’ refers to a structure thatfilters light or converts light, or both, and can be or include one ormore of: a curable resin, a dye, a pigment, a color-conversion material,a semiconductor crystal, a phosphor, and a quantum dot.

Various embodiments of the present invention can include micro-transferprintable structures, source wafers on or in which micro-transferprintable structures are made, destination substrates on whichmicro-transfer printable structures are micro-transfer printed, ormethods of making the micro-transfer printable structures, sourcewafers, or destination substrates. As used herein, a source wafer is awafer from which devices or structures formed on or in the source waferare micro-transfer printed to a destination wafer.

Color Filter

In certain embodiments of the present invention and referring to FIGS.1A and 1B, a micro-transfer printed color-filter structure 20 comprisesa color filter 22 and a fractured color-filter tether 24 physicallyattached to the color filter 22. A fractured tether is a tether that isbroken, fractured, or cracked by pressure from a transfer stamp in theprocess of micro-transfer printing. A tether physically attached to anelement is a tether that is attached to the element or physicallyattached to one or more single or multiple layers, structures,multi-layers, or multi-component structures over, on, or in contact withor supporting or protecting the element. As shown in FIG. 1A, thefractured color-filter tether 24 can include at least some of the samematerial as the color filter 22. In an embodiment, the fracturedcolor-filter tether 24 and the color filter 22 are part of a commoncolor-filter layer 28. The fractured color-filter tether 24 is a portionof the color-filter layer 28 and the color filter 22 is a portion of thecolor-filter layer 28 separate from the fractured color-filter tether24. Alternatively, as shown in FIG. 1B, the color-filter structure 20includes an encapsulation layer 31 that also forms the color-filtertether 24. The color-filter tether 24 can have a thickness that isthinner than the color filter 22. The micro-transfer printedcolor-filter structure 20 can be a resin or polymer, for example a curedresin or polymer cured by heat or electromagnetic radiation, impregnatedwith color-filter materials such as dyes, pigments, phosphors, orquantum dots. The encapsulation layer 31 can be an oxide such as silicondioxide or a nitride such as silicon nitride.

Referring to FIGS. 2A and 2B in a related embodiment, a color-filtersource wafer 26 comprises a source wafer 80 having a patternedsacrificial layer 82 including sacrificial portions 84 separated byanchors 94. The source wafer 80 can be a semiconductor, silicon, glass,plastic, resin, or polymer substrate or wafer and can include layersformed on a substrate. The sacrificial portions 84 can be a designatedportion of an anisotropically etchable silicon or a selectively etchablematerial and the anchors 94 include portions of the source wafer 80between the sacrificial portions 84. The color-filter layer 28 caninclude patterned color-filter material disposed on the patternedsacrificial layer 82 that form color filters 22 disposed entirely oneach sacrificial portion 84 and provides an opening over eachsacrificial portion 84. The anchor 94 can include portions of thecolor-filter layer 28 physically connected to the color-filter tethers24. The color-filter layer 28 can include a cured photo-curablematerial.

As shown in FIG. 2A, one or more color-filter tethers 24 physicallyconnect each color filter 22 to an anchor 94 and physically connectseach color filter 22 to an anchor 94. The color-filter tether 24 caninclude at least some of the same material as the color filter 22 andcan be part of a common color-filter layer 28. As shown in FIG. 2B, anencapsulation layer 31 encapsulates the color filter 22. A portion ofthe encapsulation layer 31 forms at least a part of the color-filtertether 24. The encapsulation layer 31 can be an oxide such as silicondioxide or a nitride such as silicon nitride deposited and patternedusing photolithographic processes.

Referring also to FIG. 3, a method of making a color-filter source wafer26 according to embodiments of the present invention comprises providinga source wafer 80 having a patterned sacrificial layer 82 includingsacrificial portions 84 separated by anchors 94 in step 200, disposing acolor-filter layer 28 on the source wafer 80 in step 210, and patterninga color filter 22 entirely on each sacrificial portion 84 in step 220.For example, the color-filter layer 28 can be disposed on the patternedsacrificial layer 82 in step 210 by coating, for example, spin coatingor curtain coating, and patterned in step 220 by exposing thecolor-filter layer 28 to electromagnetic energy (for example,ultra-violet light) through a patterned mask and washing away theuncured (unexposed) photo-curable material. Optionally, an encapsulationlayer 31 is deposited, for example by sputtering or evaporation, andpatterned in step 225, using photolithographic methods and materials. Instep 230, in an embodiment, the sacrificial portion 84 is etched to formone or more color-filter tethers 24 physically connecting each colorfilter 22 to an anchor 94. Etching can be accomplished, for example, byexposing the sacrificial portion 84 to an acid that selectively etchesthe sacrificial portion 84 material or anisotropically etches thesacrificial portion 84 in preference to the anchors 94. In step 240, acolor filter 22 is micro-transfer printed from the color-filter sourcewafer 26 to a destination substrate, such as a display substrate, bypressing a stamp, such as a PDMS stamp against the color-filterstructure 20 to fracture the color-filter tether 24, adhere thecolor-filter structure 20 to the stamp, transport the stamp and thecolor-filter structure 20 to the destination substrate and adhere thecolor-filter structure 20 to the destination substrate, and remove thestamp. The destination substrate can include an adhesive layer that isthen cured to permanently adhere the color-filter structure 20 to thedestination substrate.

LED with Color Filter

In another embodiment of the present invention and referring to FIGS. 4Aand 4B, a micro-transfer printed pixel structure 30 comprises alight-emitting diode (LED) 33 having a light-emitting side 39, a colorfilter 22 disposed adjacent to the light-emitting side 39 of the LED 33,and a fractured pixel tether 34 physically attached to the LED 33 or afractured pixel tether 34 physically attached to the LED 33 and to thecolor filter 22 or layers disposed on the LED 33 or color filter 22. Acolor filter 22 is adjacent to the light-emitting side 39 of the LED 33if it is closer to the light-emitting side 39 of the LED 33 than anyother side of the LED 33 and if it is located in optical associationwith LED 33 to absorb or transmit light emitted by the LED 33. A colorfilter 22 can be in contact with, formed on, or adhered to an LED 33 andcan be physically located within 0 to 250 microns of the LED 33. Thecolor filter 22 can be formed in a layer that is essentially planar orhas opposing planar surfaces. The color filter 22 can be a semiconductorcrystal structure.

In a further embodiment of the present invention, the LED 33 is a partof an LED structure 32 that includes a fractured LED tether 35 disposed,for example, by micro-transfer printing the LED 33 from an LED sourcewafer onto the color filter 22. The LED structure 32 can includepatterned dielectric structures 37 that electrically isolate portions ofthe LED 33 and expose other portions of the LED 33 that are electricallyconnected to electrodes 38. The electrodes 38 can provide electricalpower to the LED 33 to cause the LED 33 to emit light, for examplethrough the light-emitting side 39 and through the color filter 22, sothat the LED structure 32 emits color-filtered light.

The fractured pixel tether 34 can be the fractured color-filter tether24 and can include at least some of the same material as the colorfilter 22, as shown in FIG. 4A. The color filter 22 and the color-filtertether 24 can be a color-filter structure 20. Alternatively, as shown inFIG. 4B, an encapsulation layer 31 can encapsulate the LED 33 and colorfilter 22 and form a part of the fractured pixel tether 34 or thefractured pixel tether 34 can be a part of or attached to theencapsulation layer 31. In another embodiment, not shown, the colorfilter 22 is attached to a color-filter tether 24 (as in FIG. 4A) and anencapsulation layer 31 encapsulates the LED 33, the color filter 22, andthe color-filter tether 24 and also forms a part of the fractured pixeltether 34 or the fractured pixel tether 34 can be a part of or attachedto the encapsulation layer 31 (i.e., the encapsulation layer 31 of FIG.4B is applied to the structure of FIG. 4A, see FIG. 5A described below).

Referring also to FIGS. 5A and 5B, in certain embodiments of the presentinvention, a pixel structure source wafer 36 comprises a source wafer 80having a patterned sacrificial layer 82 including sacrificial portions84 separated by anchors 94. An LED 33 is disposed entirely on or overeach sacrificial portion 84. The LED 33 has a light-emitting side 39. Acolor filter 22 is disposed adjacent to the light-emitting side 39 ofthe LED 33 and is disposed entirely on or over each sacrificial portion84. One or more pixel tethers 34 physically connects each LED 33 orcolor filter 22 to an anchor 94. In the embodiment of FIG. 5A, anencapsulation layer 31 encapsulates the LED 33 and color filter 22 andforms at least a portion of the pixel tether 34 and the color-filterstructure 20 includes a color-filter tether 24 in the color-filter layer28. The pixel tether 34 can be thinner than the color-filter structure20 to facilitate fracturing. The encapsulation layer 31 can be an oxidesuch as silicon dioxide or a nitride such as silicon nitride depositedand patterned using photolithographic processes. In the embodiment ofFIG. 5B, the color-filter layer 28 forms at least a portion of the pixeltether 34. In various embodiments, the source wafer 80 is or includes aglass, a polymer, a semiconductor, or silicon. The sacrificial portions84 can be a designated portion of an anisotropically etchable silicon ora selectively etchable material, or any one of or combination of these.The fractured pixel tether 34 can include at least some of the samematerial as the color filter 22.

Referring also to FIG. 7, in an embodiment of the present invention, amethod of making a pixel structure source wafer 36 comprises providing asource wafer 80 having a patterned sacrificial layer 82 includingsacrificial portions 84 separated by anchors 94 in step 300. In step308, an LED 33 is disposed entirely on or over each sacrificial portion84, the LED 33 having a light-emitting side 39, and a color filter 22provided adjacent to the light-emitting side 39 of each LED 33. Thecolor filter 22 is also disposed entirely on or over each sacrificialportion 84 to form a pixel structure 30. The sacrificial portion 84 isetched in step 330 to form one or more pixel tethers 34 physicallyconnecting each pixel structure 30 to an anchor 94. In step 340, thepixel structure 30 is micro-transfer printed from the pixel structuresource wafer 36 to a destination substrate.

The color filter 22 and LED 33 can be provided or disposed in a varietyof ways according to a corresponding variety of embodiments of thepresent invention. In one embodiment corresponding to FIG. 5A, the colorfilter 22 is micro-transfer printed in step 301 from a color-filtersource wafer 26 onto the source wafer 80 entirely over the sacrificialportion 84 and an LED 33 is micro-transfer printed from an LED sourcewafer onto the color filter 22 in step 302 so that the color filter 22is disposed adjacent to the light-emitting side 39 of the LED 33. Thecolor filter 22 can be part of a color-filter structure 20 with afractured color-filter tether 24 as shown in FIG. 1A or 1Bmicro-transfer printed from a color-filter source wafer 26 as shown inFIG. 2A or 2B onto or over the sacrificial portion 84 of the sourcewafer 80. An encapsulation layer 31 is optionally disposed, for exampleby deposition using any of a variety of methods such as sputtering orevaporation, and can form at least a portion of the pixel tether 34.

In another embodiment corresponding to FIG. 5B, a color-filter layer 28is disposed over the patterned sacrificial layer 82, for example bycoating, in step 303 and then patterned in step 320, for example usingphotolithographic methods and materials as described above. The colorfilter 22 is patterned in step 302 on the source wafer 80 entirely overthe sacrificial portion 84 and the LED structure 32 is micro-transferprinted from an LED source wafer onto the color filter 22 in step 302 sothat the color filter 22 is disposed adjacent to the light-emitting side39 of the LED 33. The pixel tether 34 is then the same tether as thecolor-filter tether 24. Thus, the fractured pixel tether 34 can includethe LED tether 35 and can include at least some of the same material asthe color filter 22. The pixel tether 34 can also include at least someof the same material as the LED 33.

Referring to FIGS. 6A-6C, in alternative structures of the presentinvention, an optional reflective or conductive electrode 38R or layeris disposed on the sacrificial portion 84. Electrical power is providedto the LED 33 through the electrodes 38, 38R. As shown in FIGS. 6A and6B, electrodes 38 can be contacted through vias in the color-filterlayer 28. The color-filter layer 28 is patterned to form the vias andthe color filter 22 disposed adjacent to the light-emitting side 39 ofthe LED 33 in the pixel structure 30. The color-filter layer 28 canprovide the pixel tether 34 (as shown in FIG. 6A) or an encapsulationlayer 31 can be coated over the color-filter structure 20 and form atleast a portion of the pixel tether 34 (as in FIG. 6B).

A method of making a pixel structure source wafer 36 in embodimentscorresponding to FIGS. 6A and 6B, includes micro-transfer printing anLED 33 from an LED source wafer onto the source wafer 80 entirely overthe sacrificial portion 84 in step 305. The LED 33 can be part of an LEDstructure 32 including an LED tether 35. In the embodiment of FIG. 6A, acolor-filter layer 28 is coated over the LED 33 in step 307. Thecolor-filter layer 28 is patterned in step 322, for example usingphotolithography, to form a color filter 22 disposed adjacent to thelight-emitting side 39 of the LED 33. Vias can be formed in the samestep to expose the electrodes 38, 38R and the color-filter layer 28 canform the pixel tether 34 so that the pixel tether 34 is a color-filtertether 24. In the embodiment of FIG. 6B, the color-filter layer 28 ispatterned to form the color filter 22 only and an encapsulation layer 31is disposed, for example by deposition using any of a variety of methodssuch as sputtering or evaporation, to form at least a portion of thepixel tether 34. The pixel tether 34 can be thinner than the colorfilter 22 to facilitate fracturing.

In another method forming a structure shown in FIG. 6C, color filters 22are micro-transfer printed from a color-filter source wafer 26 onto theLED structure 32 in step 306 to form the pixel structure 30. The colorfilters 22 can be part of a color-filter structure 20 that includes acolor-filter tether 24. An adhesive or planarizing layer 50 can be usedto adhere the color-filter structure 20 to the LED structure 32, forexample an uncured curable encapsulation layer 31, and then cured.

Intermediate Substrate

In an embodiment of the present invention referring to FIGS. 8A and 8B,a micro-transfer printed intermediate structure 40 comprises anintermediate substrate 48 and one or more pixel structures 30 disposedon the intermediate substrate 48. Each pixel structure 30 includes anLED 33 having a light-emitting side 39, a color filter 22 disposedadjacent to the light-emitting side 39 of the LED 33, and a fracturedpixel tether 34 physically attached to the LED 33 or physically attachedto the LED 30 and to the color filter 22. The pixel structure 30 can beany of the pixel structures 30 described herein, for example includingany of the pixel structures 30 illustrate in FIGS. 4, 5A, 5B 6A, 6B, and6C and can include encapsulation layers 31 (not shown). The LED 33 canbe a part of an LED structure 32 that also includes a fractured LEDtether 35. As shown in FIG. 8A, the color filter 22 can be a part of acolor-filter structure 20 that also includes a fractured color-filtertether 24. Alternatively, as shown in FIG. 8B, the color filter 22 isnot attached to a color-filter tether 24 but is formed in place. Thefractured pixel tether 34 can be or include any of the color-filtertether 24, the LED tether 35, and a portion or materials of anencapsulation layer 31 (not shown).

A fractured intermediate tether 44 is physically attached to theintermediate substrate 48 to form a micro-transfer printed intermediatestructure 40. The intermediate substrate 48 can be or include a glass, apolymer, a semiconductor, or silicon, or any one or any combination ofthese. The fractured intermediate tether 44 can include at least some ofthe same material as the color filter 22, or at least some of the samematerial as the intermediate substrate 48, or both, or an encapsulationlayer 31 (not shown) encapsulating the LED 33 and color filter 22 canform at least a part of the fractured intermediate tether 44 or thefractured intermediate tether 44 can be a part of the encapsulationlayer 31 (similar to the structure of FIG. 5A).

Referring also to FIGS. 9A and 9B, in certain embodiments anintermediate structure source wafer 46 comprises a source wafer 80having a patterned sacrificial layer 82 including sacrificial portions84 separated by anchors 94. A patterned intermediate substrate layer 42disposed on or over the patterned sacrificial layer 82 forms separateand independent intermediate substrates 48. Each intermediate substrate48 is disposed entirely over a sacrificial portion 84. One or more pixelstructures 30 are disposed entirely on each intermediate substrate 48.Each pixel structure 30 includes an LED structure 32 having an LED 33with a fractured LED tether 35, the LED 33 having a light-emitting side39, and a color filter 22 disposed adjacent to the light-emitting side39 of the LED 33. One or more fractured pixel tethers 34 are physicallyattached to each pixel structure 30 and an intermediate tether 44 isphysically attached to the intermediate substrate 48.

In certain embodiments, the source wafer is or includes a glass, apolymer, a semiconductor, or silicon, the intermediate substrate 48 isor includes a glass, a polymer, a semiconductor, or silicon, thesacrificial portions 84 are a designated portion of an anisotropicallyetchable silicon or a selectively etchable material, or any one or anycombination of these. The fractured pixel tether 34 can include at leastsome of the same material as the color filter 22, at least some of thesame material as the LED 33, or portions of or materials from anencapsulation layer 31 encapsulating the color filter 22 and LED 33. Theintermediate tether 44 can include at least some of the same material asthe color filter 22 or some of the material from an encapsulation layer31. Alternatively, the intermediate tether 44 can include at least someof the same material as the intermediate substrate 48. In yet anotherembodiment, the intermediate tether 44 includes at least some of thesame material as the source wafer. In an embodiment, the intermediatesubstrate 48 includes portions of or materials from the color filter 22.

As shown in FIG. 9A, the color filter 22 is part of a color-filterstructure 22 including a color-filter tether 24 that is micro-transferprinted onto or over the intermediate substrate 48. Alternatively, asshown in FIG. 9B, the color filter 22 is coated and patterned usingphotolithography on the intermediate substrate 48 so that nocolor-filter tether 24 is present.

Referring also to FIG. 10A, a method of making an intermediate structuresource wafer 46 comprises providing in step 400 a source wafer having apatterned sacrificial layer 82 including sacrificial portions 84separated by anchors 94. In step 408, an intermediate substrate layer 42is disposed over the patterned sacrificial layer 82 and patterned instep 409 to form an intermediate substrate 48 entirely over eachsacrificial portion 84. In step 404, one or more pixel structures 30 aredisposed on each intermediate substrate 48 entirely on or over eachsacrificial portion 84 and intermediate substrate 48. Each pixelstructure 30 includes an LED 33 having a light-emitting side 39, a colorfilter 22 disposed adjacent to the light-emitting side 39 of the LED 33,and a fractured pixel tether 34 physically attached to the pixelstructure 30 to form an intermediate structure 40. This step is repeatedas often as desired until done in step 410, for example to dispose ared, green, and blue pixel structure 30 on the intermediate substrate48. The pixel structures can be electrically connected with wires on theintermediate substrate 48 in step 430. In this case, the intermediatestructure 40 can be a full-color pixel with improved color gamutincluding a red LED 33 emitting red light through a red color filter22R, a green LED 33 emitting green light through a green color filter22G, and a blue LED 33 emitting blue light through a blue color filter22B.

In further embodiments, the sacrificial portion 84 is etched to form oneor more intermediate tethers 44 physically connecting each intermediatestructure 40 to an anchor 94 in step 440 and an intermediate structure40 is micro-transfer printed in step 450 from the intermediate structuresource wafer 46 to a destination substrate, such as a display substrate.

In one embodiment, one or more pixel structures 30 are disposed on eachintermediate substrate 48 entirely on or over each sacrificial portion84 by micro-transfer printing a pixel structure 30 from a pixelstructure source wafer 36 onto the intermediate substrate 48 of thesource wafer 80 entirely over the sacrificial portion 84.

In other embodiments, referring to FIG. 10B, one or more pixelstructures 30 are disposed on each intermediate substrate 48 entirely onor over each sacrificial portion 84 by micro-transfer printing a colorfilter 22 in step 401 from a color-filter source wafer 26 onto theintermediate substrate 48 of the source wafer 80 entirely over thesacrificial portion 84 and then micro-transfer printing an LED 33 froman LED source wafer onto or over the color filter 22 in step 402 so thatthe color filter 22 is disposed adjacent to the light-emitting side 39of the LED 33, for example in a bottom-emitting configuration.

In another embodiment, the steps are reversed so that the color-filterstructure 20 is micro-transfer printed onto the LED structure 32. Inthis embodiment, an LED 33 is micro-transfer printed from an LED sourcewafer onto the intermediate substrate 48 of the source wafer 80 entirelyover the sacrificial portion 84 in step 405 and a color filter 22 ismicro-transfer printed from a color-filter source wafer 26 onto the LED33 in step 406 so that the color filter 22 is disposed adjacent to thelight-emitting side 39 of the LED 33 in a top-emitting configuration. Aplanarizing or adhesive layer 50 can be provided to adhere the colorfilter 22 to the LED 33 (FIG. 6C).

In yet another embodiment, an LED 33 is micro-transfer printed from anLED source wafer onto the source wafer 80 entirely over the sacrificialportion 84 and intermediate substrate 48 in step 405 and a color filter22 is formed over the LED 33 by disposing the color-filter layer 28 overthe LED 33 in step 407 and patterning the color-filter layer 28 in step422 so that the color filter 22 is disposed adjacent to thelight-emitting side 39 of the LED 33. In an alternative embodiment, acolor filter 22 is formed on the source wafer 80 entirely over thesacrificial portion 84 by disposing the color-filter layer 28 over theLED 33 in step 403, patterning the color-filter layer 28 in step 420,and micro-transfer printing an LED 33 from an LED source wafer onto thecolor filter 22 so that the color filter 22 is disposed adjacent to thelight-emitting side 39 of the LED 33 in step 402.

Display

In an embodiment of the present invention illustrated in FIG. 11, aninorganic LED display 10 includes a display substrate 12. A plurality ofpixel structures 30 (e.g., red pixel structure 30R, green pixelstructure 30G, and blue pixel structure 30B) are disposed on the displaysubstrate 12. Each pixel structure 30 includes one or more LEDs 33, eachLED 33 having a light-emitting side 39 (FIG. 4), and a color filter 22corresponding to each LED 33, each color filter 22 disposed adjacent tothe light-emitting side 39 of the corresponding LED 33. The plurality ofpixel structures 30 can include a red pixel structure 30R having a redLED 33R emitting red light through a red color filter 22R, a green pixelstructure 30G having a green LED 33G emitting green light through agreen color filter 22G, and a blue pixel structure 30B having a blue LED33B emitting blue light through a blue color filter 22B. The red, green,and blue pixel structures 30R, 30G, 30B, can form a full-color pixel 14having improved color gamut.

In a variety of embodiments corresponding to the various pixelstructures 30 and methods described above, each color filter 22 can belocated between the display substrate 12 and a corresponding LED 33 (abottom-emitter configuration) or each LED 33 can be located between thedisplay substrate 12 and a corresponding color filter 22 (a top-emitterconfiguration). Each LED 33 can be part of a micro-transfer printed LEDstructure 32 including an LED 33 having a fractured LED tether 35physically attached to the LED 33. Each color filter 22 can be part of acolor-filter structure 20 having a color a micro-transfer printed colorfilter 22 having a fractured color-filter tether 24 physically attachedto the color filter 22. Each pixel structure 30 can be a micro-transferprinted pixel structure 30 having a fractured pixel tether 34. (Tethersare not shown in FIG. 11.)

Referring to the alternative embodiment of FIG. 12, each pixel structure30 is part of an intermediate structure 40 having an intermediatesubstrate 48 and a fractured intermediate tether 44. The pixelstructures 30 can be micro-transfer printed onto the intermediatesubstrate 48 of the intermediate structure 40, so that each pixelstructure 30 includes a pixel tether 34 (FIG. 4). (Tethers are not shownin FIG. 12.)

Referring to FIG. 13, a method of making an LED display 10 comprisesproviding a display substrate 12 in step 500 and disposing a pluralityof pixel structures 30 on the display substrate 12 in step 560. Eachpixel structure 30 includes one or more LEDs 33, each LED 33 having alight-emitting side 39 (FIG. 4), and a color filter 22 corresponding toeach LED 33. Each color filter 22 is disposed adjacent to thelight-emitting side 39 of the corresponding LED 33. The pixel structures30 can be micro-transfer printed from a pixel structure source wafer 36to the display substrate 12. FIG. 15 is a simplified illustration ofsuch a structure. In step 550, substrate wires (not shown) are formed,for example photolithographically, over the display substrate 12 andelectrically connected to the LEDs 33 in the pixel structures 30.

In an alternative method as also shown in FIG. 13, intermediatestructures 40, for example each including a full-color pixel 14, aremicro-transfer printed to the display substrate 12 from an intermediatestructure source wafer 46 in step 570 and electrically connected in step550. FIG. 19 is a simplified illustration of this structure in which thecolor filter 22 is micro-transfer printed onto the intermediatesubstrate 48 and FIG. 20 is a simplified illustration of this structurein which the color filter 22 is coated and patterned on the intermediatesubstrate 48 and the LED 33 micro-transfer printed onto or over thecolor filter 22. FIG. 21 is a simplified illustration for the case inwhich the color filter 22 is coated and patterned over themicro-transfer printed LED 33 and FIG. 22 is a simplified illustrationfor the case in which the color filter 22 is micro-transfer printed overthe micro-transfer printed LED 33, for example on a planarization oradhesive layer 50.

In other embodiments, referring to FIG. 14, an LED 33 is micro-transferprinted from an LED source wafer onto the display substrate 12 in step505 and a color filter 22 is formed over the LED 33 by disposing thecolor-filter layer 28 over the LED 33 in step 507 and patterning thecolor-filter layer 28 in step 522 so that the color filter 22 isdisposed adjacent to the light-emitting side 39 of the LED 33 as shownin the simplified illustration of FIG. 17. Alternatively, a color filter22 is micro-transfer printed on the LED 33 in step 506 as shown in thesimplified illustration of FIG. 18.

In yet another embodiment, the color filter 22 is micro-transfer printedonto the display substrate 12 in step 501 and the LED 33 ismicro-transfer printed from an LED source wafer onto the micro-transferprinted color filter 22 so that the color filter 22 is disposed adjacentto the light-emitting side 39 of the LED 33 in step 502. FIG. 15 is alsoa simplified illustration of this structure.

In an alternative embodiment, a color filter 22 is formed on the displaysubstrate 12 by disposing the color-filter layer 28 over the displaysubstrate 12 in step 503, patterning the color-filter layer 28 in step520, and micro-transfer printing an LED 33 from an LED source wafer ontoor over the patterned color filter 22 in step 502 so that the colorfilter 22 is disposed adjacent to the light-emitting side 39 of the LED33. FIG. 16 is a simplified illustration of this structure.

Both the intermediate structures 40 and the pixel structures 30 can beconstructed with connection posts. For example, FIG. 23 illustrates anintermediate structure source wafer 46 including connection posts 86electrically connected to the LED 33. The encapsulation layer 31 formsthe intermediate tether. The color-filter structure 20 includes a colorfilter 20 and a fractured color-filter tether 24 that is micro-transferprinted onto the intermediate substrate 48 and the LED structure 32 ismicro-transfer printed onto the color-filter structure 20 to make apixel structure 30.

The present invention provides simple structures and methods forconstructing flat-panel displays 10 that do not require large andexpensive fabrication facilities. By employing micro-transfer printingto dispose LEDs 33, pixel structures 30, or intermediate structures 40,the need for extensive flat-panel processing tools for large substrateswith high resolution are mitigated. High-resolution processing can beperformed on smaller wafers, for example 8-inch diameter wafers or12-inch-diameter wafers using much smaller equipment.

Furthermore, the present invention provides a way to greatly reduce theamount of color-filter material used in a flat-panel display. Thefollowing example is illustrative and structure sizes are chosen forsimplicity. Photo-curable color filters and black-matrix materials inflat-panel displays (for example as in a liquid crystal display or OLEDdisplay using white-light emitting layers) are typically deposited bycoating the entire substrate and then photolithographically exposing thematerials through a mask to pattern-wise cure the materials in desiredpixel locations and then wash away the uncured material. Thus, for a onesquare meter display, one square meter of each material type isdeposited.

In contrast, according to embodiments of the present invention, aninorganic LED display 10 using micro-transfer printed color filters 22,pixel structures 30, or intermediate structures 40 uses a greatlyreduced quantity of color-filter material. In this example, a 4 kdisplay having eight million three-color pixels is presumed. Each lightemitter (LED 33) is presumed to be formed in a 20-micron by 20-microncell area on an LED source wafer including LED tethers 35 and anchor 94areas. Since the color filters 22 filter or process the light emittedfrom the LEDs 33, they are of similar size and, to enhancemicro-transfer printing efficiency, have the same spatial arrangementand pitch. For simplicity, the LEDs 33 and color filters 22 are assumedto be arranged in a rectangle of four thousand by two thousand elements,occupying a space of 8 cm by 4 cm.

In the case in which a micro-transfer printable color filter 22 is used,the color filters 22 are constructed as part of the color filter sourcewafer 26 and the minimum area of color-filter material necessary is 32square centimeters. In contrast, the conventional process requires10,000 square centimeters, resulting in a cost reduction of color-filtermaterials alone of more than 300 times (thus using 0.3% as muchmaterial). The same savings are found for the micro-transfer printedpixel structure 30 embodiments and any embodiment in which the colorfilters 22 are micro-transfer printed.

In the intermediate structure embodiment in which the color filters 22are patterned on the intermediate substrate 48 (steps 407 and 422 orsteps 403 and 420 of FIG. 10B) the coated area is larger. Presuming thatthe intermediate substrates 48 are 90 microns by 90 microns, includethree LEDs 33 and a controller integrated circuit, and are separated by10 microns on the intermediate structure source wafer 46, an area of 100microns by 100 microns is coated for each color and each pixel. In thiscase, the minimum area of color-filter material is 800 squarecentimeters, resulting in a cost reduction of color-filter materials of12.5 (using 8 percent as much material).

In the case of a 2000 by 1000 pixel display (approximately conventionalhigh definition pixel count), only 25% as much color-filter material isneeded. In contrast, in a conventional design, reducing the number ofpixels in a display having the same size substrate does not reduce theuse of color-filter materials.

The LEDs 33 can be arranged and electrically connected in rows andcolumns over the display substrate 12 to enable matrix addressing withelectrical signals supplied by passive- or active-matrix controllers.Electrical signals from the controllers can cause the LEDs 33 to emitlight.

The display substrate 12 can be polymer, plastic, resin, polyimide, PEN,PET, metal, metal foil, glass, a semiconductor, or sapphire.

Each LED 33 can be a light-emitting diode (LED), a micro-LED, a laser, adiode laser, or a vertical cavity surface emitting laser and can includeknown light-emitting diode materials and structures. The LEDs 33 cancomprise an inorganic solid single-crystal direct bandgap light emitter,can emit visible light, such as red, green, blue, yellow, or cyan light,violet, or ultra-violet light, and can emit either coherent orincoherent light. The light emitters used herein can have at least oneof a width, length, and height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm,or 20 to 50 μm. Light emitted from or through the color filters 22 canbe a very pure light and highly saturated and can have a full width halfmax (FWHM) less than or equal to 100 nm, 50 nm, or even less than orequal to 20 nm.

Various embodiments of the present invention incorporate different colorfilters and light emitters in full-color pixels 14. In one embodiment, afull-color pixel 14, for example in an intermediate structure 40includes one each of a red, green, and blue LEDs 33R, 33G, 33B withcorresponding red, green, and blue color filters 22R, 22G, 22B., asshown in FIG. 12. In other embodiments, the red pixel does not include ared color filter 22R or the red and blue pixels do not include red orblue color filters 22R, 22B, respectively. In another embodiment, a blueLED 33B is used for all of the pixels and the red and green pixelsemploy a color filter including red and green color-change materials,respectively. In yet another embodiment, an ultra-violet LED 33 is usedfor all of the pixels and the red, green, and blue pixels employ a colorfilter including red, green, and blue color-change materials,respectively. Other arrangements of light emitting LEDs 33 and colorfilters 22, including color-change materials, are possible and includedin the present invention.

A discussion of micro-LEDs 33 and micro-LED displays can be found inU.S. Provisional patent application Ser. No. 14/743,981, filed Jun. 18,2015, entitled Micro Assembled LED Displays and Lighting Elements, whichis hereby incorporated by reference in its entirety. Micro-transfermethods are described in U.S. Pat. Nos. 8,722,458, 7,622,367 and8,506,867, each of which is hereby incorporated by reference in itsentirety.

Controllable Color Filters

According to some embodiments of the present invention, color filters 22are controllable color filters 22 disposed on or over a color-filtersubstrate 72. For example, the color filters 22 can be responsive tocontrol signals such as a voltage or electric field, for example,provided between electrodes disposed on either side of the color filter22 or to heat provided to the color filters 22, where the color filters22 are at least substantially planar and have a thickness significantlyless than its extent over the color-filter substrate 72, for examplelength and width. Color filters 22 can be very thin, for example havinga thickness less than or equal to ten microns, less than or equal to onemicron, less than or equal to 100 nm, less than or equal to 50 nm, orless than or equal to 20 nm. In certain embodiments, color filters 22are controlled to absorb, transmit, or reflect different colors oflight. Color filters 22 can include optical spacers to enableconstructive and destructive optical interference at desiredfrequencies. Color filter 22 and optical spacers can be deposited andpatterned using photolithographic methods and materials.

In some embodiments, referring to FIGS. 24A, 24B, and 25, a color-filterdevice 99 comprises a color filter 22 and at least one electricalconductor 38 disposed in contact with the color filter 22. At least aportion of a color-filter tether 24 is attached to the color filter 22or structures formed in contact with or supporting the color filter 22.A color-filter tether 24 can also be a pixel tether 34 (as shown inFIGS. 27A, 27B) and can be broken (e.g., fractured) (as shown in FIGS.24A, 24B, and 25).

In certain embodiments, because the color filters 22 are controllable,they are variable color filters 22 that can change their opticalattributes, such as color, transparency, absorption, or reflectivity. Insome embodiments, a color filter 22 is or includes one or more of: aphase-change material, an ink, a gel, a metallopolymer material, or aphotonic crystal. In some embodiments, the color filter 22 includesphotonic crystals embedded within an electroactive polymer. Other usablecolor-filter materials include germanium-antimony-tellurium (GST). Forexample, in certain embodiments, a color-filter comprising GST canchange phase with applied voltage of less 10 volts amplitude and asub-millisecond duration. In some embodiments, the color filter 22includes additional optical layers or structures, for example spacinglayers, to optimize the optical effect of the controllable color-filtermaterial. The color filter 22 can include multiple layers of differentmaterials, for example multiple layers of controllable materials and oneor more optical spacer layers, to provide a wide range of potentialstates and colors.

In certain embodiments, a color filter 22 can be electricallycontrolled. According to some embodiments of the present invention, thecolor-filter material is a phase-change material that can be controlledto switch, for example, from an amorphous state to a crystalline stateor from a crystalline state to an amorphous state. Each of the amorphousstate and the crystalline state can have a different optical attribute,such as color. In some embodiments, a single color filter 22 can becontrolled to have a variety of colors.

Referring to FIGS. 24A and 24B, a color-filter device 99 comprises theelectrical conductor 38, for example a bottom electrode 38M (FIG. 24A)or top electrode 38T (FIG. 24B) that is resistive or has a portion thatis a resistive electrode 38V and is heated when electrical current flowsthrough the resistive electrode 38V. The resistive electrode 38V can be,for example a metal or metal alloy, such as aluminum, or asemiconductor. The heated resistive electrode 38V then heats the colorfilter 22 in response to the electrical current passed through theresistive electrode 38V. In some embodiments, a color filter 22 is orincludes a phase-change material that changes the color of lightfiltered by the color filter 22 in response to heat.

In some embodiments, an electrical conductor 38 or resistive electrode38V is substantially transparent and allows visible light to passthrough. Light 70A incident on the color filter 22 is transmittedthrough the resistive electrode 38V and passes through the color filter22 once. In some embodiments, an electrical conductor 38 or resistiveelectrode 38V is substantially reflective and reflects visible light.Light 70B incident on the color filter 22 is reflected by the resistiveelectrode 38V, passing through the color filter 22 twice. In someembodiments, a color filter 22 is a reflective color filter 22 andreflects light itself. In some embodiments, a color filter 22 is atransmissive color filter 22 and transmits light. In some embodiments ofthe present invention, a transparent electrode transmits more than 50%of the light incident on the transparent electrode (e.g., more than 70%,80%, 90%, or 95%) and a reflective electrode reflects more than 50% thelight incident on the reflective electrode (e.g., more than 70%, 80%,90%, or 95%). A reflective electrode can be a metal or metal alloy, suchas aluminum, silver, titanium, or tin or alloys thereof. Transmissiveelectrodes can be thin metal or metal alloys or transparent metal oxidessuch as indium tin oxide.

In some embodiments of the present invention, referring to FIG. 25, thecolor filter 22 has a first side 21 a and a second side 21 b opposed tothe first side 21 a, the electrical conductor 38 is a first electrode38M disposed on the first side 21 a of the color filter 22, and a secondelectrode 38T is disposed on the second side 21 b of the color filter 22and is part of another electrical conductor 38. In various embodiments,both the first and second electrodes 38M, 38T are transparent, the firstelectrode 38M is transparent and the second electrode 38T is reflective,or alternatively the second electrode 38T is transparent and the firstelectrode 38M is reflective. In such various embodiments, the colorfilter 22 can alter the color of light that it transmits, reflects, orabsorbs in response to an electrical current, a voltage, or anelectrical field provided between the first and second electrodes 38M,38T.

In some embodiments, for example, the illustrative embodiments of FIG.24A, FIG. 24B, or FIG. 25, the electrical current or voltage can beprovided by a controller, e.g., an electronic circuit, provided on thecolor-filter substrate 72 or a controller external to a color-filterdevice 99 or color-filter substrate 72 (e.g., a micro-transfer printablecolor-filter device or substrate). However, some variable andcontrollable color-filter materials require a relatively large amount ofcurrent to change their state, for example if the color-filter materialrequires heating or a high current density. In large-area devices thiscan be a problem, since much applied power is lost via substrateinterconnect wiring and therefore requires a very large drive currentand voltage that result in significant substrate heating. According tosome embodiments of the present invention, this problem can be mitigatedby providing charge storage locally to each color filter 22 or group ofcolor filters 22.

Referring to FIG. 26A, in certain embodiments, for example, a controlcircuit 66 comprises a switch 60, for example a transistor, controllablyconnecting a capacitor 62 to an electrical conductor 38 (e.g., resistiveelectrode 38V, first electrode 38M, or second electrode 38T). Thecapacitor 62 stores charge provided through electrical connections toground and V_(dd) power supplies. The capacitor 62 can be charged for arelatively long period of time at a low current rate through theinterconnect wiring, then discharged relatively quickly and at highcurrent density into the color filter 22 or a heater disposed adjacentto the color filter 22 (e.g., the resistive electrode 38V) by a localtransistor (e.g., switch 60) over very short interconnects inside thepixel. Such a control method using low current-drive voltage can be veryprecise, and can provide sufficient control of the color-filter materialstate conversion. In some embodiments, the color filter 22 is convertedto a crystalline state with a smaller amplitude and longer termelectrical pulse and converted to an amorphous state with a largeramplitude and shorter term electrical pulse, for example at 10 volts.

In certain embodiments, when a control signal turns on the switch 60,the capacitor 62 discharges through the resistive electrode 38V (bottomelectrode 38M as shown in FIG. 24A). Alternatively, the switch 60 canprovide power to the top electrode 38T or bottom electrode 38M (but notboth) while the other electrode is grounded. In certain embodiments, acapacitor 62 stores power locally to each color filter 22 on thecolor-filter substrate 72. In certain embodiments, by providing localcapacitors 62, the instantaneous current passing through the power linesis reduced. In certain display applications, local capacitors 62 can becharged once per frame update rather than once per line or pixel update,reducing the current flow density through the power lines by a factorcorresponding to the number of lines or pixels. This can greatly reducelosses due to resistance and increase the maximum frame rate of adisplay using a color-filter devices 99 (e.g., a micro-transfercolor-filter device) in accordance with certain embodiments of thepresent invention. In some embodiments of the present invention, thecontrol circuit 66 is disposed underneath the bottom electrode 38M sothat the extent of the color filter 22 over the color-filter substrate72 includes the control circuit 66, enabling a large fill factor for thecolor-filter device 99. In a reflective display application, anincreased fill factor can improve display contrast.

Referring to FIG. 26B, a circuit in accordance with the illustrativeembodiment of FIG. 26A can additionally include another switch(isolation switch 61) that isolates the power supply from the capacitor62. The isolation switch 61 can be turned on when the control switch 60is turned off and can be turned off when the control switch 60 is turnedon. This enables precise control of the amount of charge deposited inthe capacitor 62 and the charge that is applied to the resistiveelectrode 38V, resulting in very precise heating or other control of thecharacteristics of the load (e.g., resistive electrode 38V). The use ofan isolation switch 61 enables more relaxed control and timing signalsand eliminates the effect of the load from the V_(dd) power supply andwiring thereby keeping the V_(dd) across the array at a more stablevoltage. The isolation switch 61 characteristics such as transistorwidth and length can be chosen to limit the current into the capacitor62 thereby minimizing voltage drops on V_(dd) and stabilizing the V_(dd)across the array. A lower, more even current is applied during chargingand the sharp high current impulse into the load is isolated from theV_(dd) supply.

As shown in FIG. 26C, in certain embodiments, two different powersupplies, V_(dd1) and V_(dd2), are provided, each with a separateisolation switch 61, that are alternatively controlled and can providedifferent amounts of power or voltage to the load. One isolation switch61 provides a connection to a V_(dd1) power supply for one statetransition (e.g., a transition to a crystalline state), and the otherisolation switch 61 provides a connection to a V_(dd2) power supply fora second state transition (e.g., a transition to an amorphous state). Incertain embodiments, this can be necessary in a system where selectionbetween amorphous and crystalline states would need to be madesimultaneously. In certain embodiments, such circuits allow thecapacitor voltage to be set appropriately for each state transitionwithout requiring adjustment of the single V_(dd) between the states.

As also shown in FIG. 26C, in certain embodiments, a color-filter device99 (e.g., a micro-transfer color-filter device) can include a readoutterminal that, in some embodiments, also includes an isolation switch61. When turned on, typically when a control switch 60 is turned off, areadout circuit can detect a change in permittivity and/or conductivityof a color-filter device 99 which is an indication of amorphous orcrystalline color-filter material state. This structure already existsfor a color-filter device 99 that uses the color-filter material as itsown heater via current conduction through the color-filter material. Thereadout circuits can sense a change in permittivity/conductivity of acolor-filter material, for example, by measuring current through, orvoltage across, a resistive electrode 38V. In some embodiments of thepresent invention, a color filter 22 has two states, a programmedcrystal state and an erased amorphous state. Without wishing to be boundto any particular theory, in general, changing a color filter 22 to acrystalline state is more difficult. Therefore, if states areinterpreted in an application as a valid or invalid indicator, it can beuseful to consider the crystal state as valid and the amorphous state asinvalid, since any unauthorized tampering can more easily convert thecolor filter 22 from the crystal (valid) to amorphous (invalid) statethan the reverse. In some embodiments of the present invention, localcircuits can be added to each color-filter device 99 to detect the stateof the color filter 22.

Referring to FIG. 27A, in certain embodiments, a color-filter device 99can comprise a plurality of color filters 22 disposed on a commoncolor-filter substrate 72. Each color filter 22 of the plurality ofcolor filters 22 can have an electrically separate electrical conductor38 disposed in contact with the color filter 22. The color of lightfiltered by each color filter 22 of the plurality of color filters 22 isa different color of light from the color of light filtered by othercolor filters 22 of the plurality of color filters 22. For example, asshown in FIG. 27A, a color-filter device 99 includes three color filters22, each controllably filtering a different color of light, for examplered, green, and blue, to form a pixel in a display 10 (as shown in FIGS.11 and 12). The color filters 22 and the electrical conductors 38 on thecolor-filter substrate 72 can be disposed on the display substrate 12(as shown in FIG. 11). As shown in FIG. 26A, each color filter 22 canhave a capacitor 62 and switch 60. Alternatively, a common capacitor 62can be provided for the group of color filters 22 in the color-filterdevice 99 (e.g., as in FIG. 27A) and controllably connected throughindividual switches 60 to each of the color filters 22 in thecolor-filter device 99.

In certain embodiments, referring to FIG. 27B, a plurality ofcolor-filter devices 99 are disposed on an intermediate substrate 48that is separate from the color-filter substrates 72. The intermediatesubstrates 48 are disposed on the display substrate 12 (as shown in FIG.12). Each color filter 22 can have an attached color-filter tether 24 sothat the color filters 22 can be, but are not necessarily,micro-transfer printed from a color filter source wafer 80 to theintermediate substrate 48. Moreover, the intermediate substrate 48 canhave an intermediate tether 44 so that the intermediate substrate 48itself can be, for example, micro-transfer printed to a destination ordisplay substrate 12. The intermediate tether 44 can be a portion of orattached to the intermediate substrate 48 or a layer or structure formedon, in, over, or under the intermediate substrate 48.

Referring to FIG. 28A, in certain embodiments, a color-filter device 99can be formed or provided on a source wafer 80. The source wafer 80 hasa substrate comprising a sacrificial layer 82 with patterned sacrificialportion 84 separate by anchors 94. One or more micro-transfer colorfilters 22 are disposed entirely over each sacrificial portion 82. Asshown in FIG. 28A, a color-filter device source wafer 80 can comprise aplurality of color filters 22 disposed adjacent to each other in acommon plane. Each color filter 22 of the plurality of color filters 22has an electrically separate electrical conductor 38 disposed in contactwith the color filter 22. In some embodiments, each of the differentcolor filters 22 can be made on a different color-filter device sourcewafer 80, thereby simplifying the manufacturing process, reducing costsand improving quality or yield of the color filters 22. In someembodiments, referring to FIG. 28B, a color-filter device 99 cancomprise a plurality of color filters 22 and electrical conductors 39disposed in a stack entirely over each sacrificial portion 82. In theillustrative embodiment shown in FIG. 28C, the color filters 22 aredisposed in a stack entirely over each sacrificial portion 82 and have acommon electrical conductor 38.

Referring to FIGS. 29 and 30, a micro-transfer printable color-filterdevice 99 can include connection posts 86 on a side of the color-filtersubstrate 72 opposite the color filters 22. The connection posts 86 areelectrically connected through vias in the color-filter substrate 72 tothe electrical conductor 38 and are formed in a process similar to thatof FIG. 23. A form for each connection post 86 is formed by etchingmaterial in the sacrificial portion 84, for example, pyramidalstructures having planes at an angle of 57 degrees, patterning a metallayer over the forms to make the posts, depositing and, for example,patterning the color-filter substrate 72 to make vias, and patterning ametal layer to electrically connect the connection posts 86 to theelectrical conductor 38. FIG. 29 differs from FIG. 30 in that the viasin FIG. 30 are beneath the color filters 22, thereby reducing the areaof the color-filter device 99 that is not covered with the color filter22 and increasing the fill factor (aperture ratio) of the color-filterdevice 99. A large fill factor (percent of the device area covered withthe color filter 22) is desirable to improve the contrast of acolor-filter device 99.

In some embodiments, as shown in FIG. 31, micro-transfer printablecolor-filter devices 99 of a color-filter wafer have first and secondelectrodes 38M, 38T that are used in accordance with the electrodes ofthe illustrative embodiment shown in FIG. 25. FIG. 32 shows anillustrative embodiment in which the first and second electrodes 38M,38T are electrically connected to connection posts 86. In all of theillustrative embodiments of FIGS. 29-32, an encapsulation layer 31protects the color filter 22 and a portion of the encapsulation layer 31can serve as the color-filter tether 24. In some embodiments, a portionof a color-filter substrate 72 can serve as the color-filter tether 24.A color filter 22 can be formed in place over sacrificial portions 84.In some embodiments in accordance with FIG. 27, color-filter devices 99are micro-transfer printed onto an intermediate substrate 48 over asacrificial portion 84 that, when etched forms an intermediate tether44. FIG. 32 illustrates a color-filter device 99 with connection posts86.

According to some embodiments of the present invention, display 10comprises a display substrate 12 with a plurality of color-filterdevices 99 disposed on the display substrate 12. Each color-filterdevice 99 can comprise one or more color filters 22, each color filter22 of the one or more color filters 22 having an electrically separateelectrical conductor 38 disposed in contact with the color filter 22,and the color of light filtered by each color filter 22 of the one ormore color filters 22 is a different color of light from the color oflight filtered by other color filters 22 of the plurality of colorfilters 22 in the color-filter devices 99 so that the color-filterdevices 99 form pixels disposed on the display substrate 12. In someembodiments, color-filter devices 99 are disposed on intermediatesubstrates 48 separate and independent of the display substrate 12 andcolor-filter substrates 72. In some embodiments, each color-filterdevice 99 includes multiple color filters 22 corresponding to thedifferent colors of a display and forming a color pixel. In someembodiments, different color-filter devices 99 have different colorfilters 22 and multiple different color-filter devices 99 form a colorpixel. Different color filters 22 can be sourced from differentcolor-filter device source wafers 80.

In some embodiments of the present invention, for example, referring toFIG. 33, control circuits 66 comprising electrical contacts 68, forexample, the control circuit 66 of FIG. 26A having a switch 60 andoptional capacitor 62, are provided on or in a color-filter substrate72. In certain embodiments, control circuit 66 comprises electricalcontacts 68 for providing a controlled current/voltage to the top andbottom electrodes 38T, 38M (i.e., through pixel control circuit 66) frominput current/voltage from electrodes 38 and connection posts 86. Insome embodiments, as shown in FIG. 33, the color-filter substrate 72 isa semiconductor substrate and the pixel control circuit 66, for examplethe circuit of FIG. 26A, is formed in or on the color-filter substrate72 using integrated circuit and photolithographic methods and materials.In some embodiments, the control circuits 66 are provided bymicro-transfer printing an integrated circuit having the pixel controlcircuit 66 therein onto the device substrate 48 (not shown). In someembodiments, the intermediate substrate 48 is a semiconductor substrateand the pixel control circuit 66 is formed in or on the intermediatesubstrate 48 using integrated circuit and photolithographic methods andmaterials. Control circuit(s) 66 can be micro-transfer printed onto theintermediate substrate 48.

Referring to FIG. 34, in some embodiments of the present invention, amethod of making a color-filter device display 10 comprises providing acolor-filter device source wafer 80 in step 600, providing a displaysubstrate 12 in step 610, and micro-transfer printing the micro-transferprintable color-filter devices 99 of the color-filter device sourcewafer 80 from the color-filter device source wafer 80 to the displaysubstrate 12 in step 620. In optional step 605, a capacitor 62 or switch60, or both, are micro-transfer printed to the display substrate 12 incorrespondence with each micro-transfer color-filter device 99.Alternatively, in optional step 625, a capacitor 62 or switch 60, orboth, is micro-transfer printed to each of the micro-transfercolor-filter devices 99 on the color-filter device source wafer 80. Insome embodiments of the present invention, the display substrate 12 is aflexible substrate, for example comprising polymer or plastic.

The intermediate or pixel structures 40 of the present invention can beconstructed using compound micro-assembly techniques. A discussion ofcompound micro-assembly structures and methods is provided in U.S.patent application Ser. No. 14/822,868 filed Aug. 10, 2015, entitledCompound Micro-Assembly Strategies and Devices, which is herebyincorporated by reference in its entirety.

The display substrate 12, LEDs 33, and color filters 22 can all beprovided at the same or at different times and in any order.

In general, structures, features, and elements of the present inventioncan be made using photolithographic methods and materials found in theintegrated circuit arts, the light-emitting diode arts, and the laserarts, for example including doped or undoped semiconductor materials,optically pumped crystals, conductors, passivation layer, electricalcontacts, and controllers.

As is understood by those skilled in the art, the terms “over” and“under” are relative terms and can be interchanged in reference todifferent orientations of the layers, elements, and substrates includedin the present invention. For example, a first layer or device on asecond layer, in some implementations means a first layer or devicedirectly on and in contact with a second layer. In other implementationsa first layer or device on a second layer includes a first layer ordevice and a second layer with another layer there between.

Having described certain implementations of embodiments, it will nowbecome apparent to one of skill in the art that other implementationsincorporating the concepts of the disclosure may be used. Therefore, theinvention should not be limited to the described embodiment, but rathershould be limited only by the spirit and scope of the following claims.

Throughout the description, where apparatus and systems are described ashaving, including, or comprising specific components, or where processesand methods are described as having, including, or comprising specificsteps, it is contemplated that, additionally, there are apparatus, andsystems of the disclosed technology that consist essentially of, orconsist of, the recited components, and that there are processes andmethods according to the disclosed technology that consist essentiallyof, or consist of, the recited processing steps.

It should be understood that the order of steps or order for performingcertain action is immaterial so long as the disclosed technology remainsoperable. Moreover, two or more steps or actions in some circumstancescan be conducted simultaneously. The invention has been described indetail with particular reference to certain embodiments thereof, but itwill be understood that variations and modifications can be effectedwithin the spirit and scope of the invention.

The mention herein of any publication, for example, in the Backgroundsection, is not an admission that the publication serves as prior artwith respect to any of the claims presented herein. The Backgroundsection is presented for purposes of clarity and is not meant as adescription of prior art with respect to any claim. Headers are providedfor the convenience of the reader and are not intended to be limitingwith respect to the claimed subject matter.

PARTS LIST

-   10 display-   12 display substrate-   14 pixel-   20 color-filter structure-   21 a first side-   21 b second side-   22 color filter-   22R red color filter-   22G green color filter-   22B blue color filter-   24 color-filter tether-   26 color-filter source wafer-   28 color-filter layer-   30 pixel structure-   30R red pixel structure-   30G green pixel structure-   30B blue pixel structure-   31 encapsulation layer-   32 LED structure-   33 LED-   33R red LED-   33G green LED-   33B blue LED-   34 pixel tether-   35 LED tether-   36 pixel structure source wafer-   37 dielectric structure-   38 electrode/electrical conductor-   38R reflective electrode-   38M bottom electrode/first electrode-   38T top electrode/second electrode-   38V resistive electrode-   39 light-emitting side-   40 intermediate structure-   42 intermediate substrate layer-   44 intermediate tether-   46 intermediate structure source wafer-   48 intermediate substrate-   50 planarizing layer-   60 switch-   61 isolation switch-   62 capacitor-   66 control circuit-   68 electrical contact-   70A, 70B light-   72 color-filter substrate-   80 source wafer-   82 sacrificial layer-   84 sacrificial portion-   86 connection post-   94 anchor-   99 color-filter device (e.g., micro-transfer printable color-filter    device)-   200 provide source wafer step-   210 dispose color filter layer on source wafer step-   220 pattern color filter layer step-   225 optional form patterned encapsulation step-   230 etch sacrificial portion step-   240 micro-transfer print color filter step-   300 provide source wafer step-   301 micro-transfer print color filter on sacrificial portion step-   302 micro-transfer print LED on color filter step-   303 dispose color filter on sacrificial layer step-   305 micro-transfer print LED on sacrificial portion step-   306 micro-transfer print color filter on LED step-   307 dispose color filter on LED step-   308 micro-transfer print LED and dispose color filter step-   320 pattern color filter layer step-   322 pattern color filter layer step-   330 etch sacrificial portion step-   340 micro-transfer print color filter step-   400 provide source wafer step-   401 micro-transfer print color filter on sacrificial portion step-   402 micro-transfer print LED on color filter step-   403 dispose color filter on sacrificial layer step-   404 dispose pixel structure on intermediate substrate step-   405 micro-transfer print LED on sacrificial portion step-   406 micro-transfer print color filter on LED step-   407 dispose color filter on LED step-   408 dispose intermediate substrate layer on source wafer step-   409 pattern intermediate substrates step-   410 done step-   420 pattern color filter layer step-   422 pattern color filter layer step-   430 form intermediate substrate wires step-   440 etch sacrificial portion step-   450 micro-transfer print intermediate structure on display substrate    step-   500 provide display substrate step-   501 micro-transfer print color filter on sacrificial portion step-   502 micro-transfer print LED on color filter step-   503 dispose color filter on sacrificial layer step-   505 micro-transfer print LED on sacrificial portion step-   506 micro-transfer print color filter on LED step-   507 dispose color filter on LED step-   520 pattern color filter layer step-   522 pattern color filter layer step-   550 micro-transfer print intermediate structure onto display    substrate step-   560 micro-transfer print pixel structure onto display substrate step-   570 micro-transfer print intermediate substrate onto display    substrate step-   600 provide color-filter device wafer step-   605 micro-transfer print switch onto device wafer step-   610 provide display substrate step-   620 micro-transfer print devices onto display substrate step-   625 micro-transfer print switch onto display substrate step

1. A color-filter device, comprising: a color filter; an electricalconductor disposed in contact with the color filter; and at least aportion of a color-filter tether attached to the color filter orstructures formed in contact with or supporting the color filter,wherein the color filter is a variable color filter.
 2. The color-filterdevice of claim 1, wherein the color filter is or comprises one or moreof: a phase-change material, an electrically controlled ink, a gel, aphotonic crystal, or a matrix of photonic crystals.
 3. The color-filterdevice of claim 1, wherein the electrical conductor is a resistor thatheats the color filter in response to an electrical current passedthrough the resistor and wherein the color filter changes the color oflight filtered by the color filter in response to heat received from theelectrical conductor.
 4. The color-filter device of claim 3, wherein theelectrical conductor is substantially reflective.
 5. The color-filterdevice of claim 1, wherein the color filter has a first side and asecond side opposed to the first side, the electrical conductor is afirst electrode disposed on the first side of the color filter, and thecolor-filter device comprises a second electrode disposed on the secondside of the color filter, wherein the color filter changes the color oflight filtered by the color filter in response to (i) an electricalcurrent, (ii) a voltage difference between the first and secondelectrodes, or (iii) an electrical field between the first and secondelectrodes.
 6. The color-filter device of claim 1, wherein the colorfilter is a stacked color filter.
 7. The color-filter device of claim 1,comprising two or more color filters each disposed in contact with atleast one electrically separate electrical conductor, wherein the two ormore color filters are disposed in a stacked configuration.
 8. Thecolor-filter device of claim 1, wherein the color filter is a reflectivecolor filter or a transmissive color filter.
 9. The color-filter deviceof claim 1, comprising a capacitor and a switch, the switch controllablyconnecting the capacitor to the electrical conductor.
 10. Thecolor-filter device of claim 1, comprising a color-filter substrate onor over which the color filter and electrical conductor are disposed andwherein the switch and the capacitor form a control circuit that isdisposed on or formed in the color-filter substrate and is locatedadjacent to or under the color filter.
 11. The color-filter device ofclaim 1, comprising a plurality of color filters, each color filter ofthe plurality of color filters having an electrically separateelectrical conductor disposed in contact with the color filter, whereinthe color of light filtered by each color filter of the plurality ofcolor filters is a different color of light from the color of lightfiltered by other color filters of the plurality of color filters. 12.The color-filter device of claim 11, comprising a capacitor and aplurality of switches, each switch corresponding and electricallyconnected to an electrical conductor of a different color filter tocontrollably connect the capacitor to the electrical conductor.
 13. Thecolor-filter device of claim 1, comprising a color-filter substrate on,in, over, or under which the electrical conductor and the color filterare disposed.
 14. The color-filter device of claim 13, comprising anintermediate substrate comprising an intermediate tether and wherein thecolor-filter substrate is disposed on the intermediate substrate or alayer or structure formed on, in, over, or under the intermediatesubstrate.
 15. A color-filter device wafer, comprising: a wafercomprising a wafer substrate, the wafer substrate comprising a patternedsacrificial layer including sacrificial portions separated by anchors;and a color-filter device disposed entirely over each sacrificialportion, wherein the color-filter device comprises: a color filter, anelectrical conductor disposed in contact with the color filter, and atleast a portion of a color-filter tether attached to the color filter orstructures formed in contact with or supporting the color filter,wherein the color filter is a variable color filter.
 16. Thecolor-filter device wafer of claim 15, comprising a plurality ofvariable color filters, each comprising at least a portion of acolor-filter tether, disposed entirely over each sacrificial portion,each color filter of the plurality of color filters having anelectrically separate electrical conductor disposed in contact with thecolor filter, wherein the color of light filtered by each color filterof the plurality of color filters is a different color of light from thecolor of light filtered by other color filters of the plurality of colorfilters.
 17. A color-filter device display, comprising: a displaysubstrate; a plurality of color-filter devices disposed on the displaysubstrate, wherein each color-filter device comprises one or morevariable color filters, each comprising at least a portion of acolor-filter tether, each color filter of the one or more color filtershaving an electrically separate electrical conductor disposed in contactwith the color filter, wherein the color of light filtered by each colorfilter of the one or more color filters is a different color of lightfrom the color of light filtered by other color filters of the pluralityof color filters.
 18. The color-filter device display of claim 17,comprising a plurality of color-filter substrates, each micro-transfercolor-filter device disposed on a color-filter substrate.
 19. A methodof making a color-filter device display, comprising: providing acolor-filter device source wafer, wherein the color-filter device sourcewafer comprises a wafer comprising a wafer substrate, the wafersubstrate comprising a patterned sacrificial layer including sacrificialportions separated by anchors; and a color-filter device disposedentirely over each sacrificial portion, wherein the color-filter devicecomprises: a color filter, an electrical conductor disposed in contactwith the color filter, and at least a portion of a color-filter tetherattached to the color filter or structures formed in contact with orsupporting the color filter, wherein the color filter is a variablecolor filter; providing a display substrate; and micro-transfer printingthe color-filter devices of the color-filter device source wafer fromthe color-filter device source wafer to the display substrate.
 20. Themethod of claim 19, comprising micro-transfer printing a capacitor orswitch, or both, to the display substrate in correspondence with eachcolor-filter device or micro-transfer printing a capacitor or switch, orboth, to each of the color-filter devices on the color-filter devicewafer.